1. Field of the Invention
The invention relates to an apparatus for and a method of producing proof prints on which the correctness of page impositions can be checked.
2. Description of Related Art
In the printing industry it is usually necessary to verify data files before printing plates for a printing press are produced. Such a verification, which is also referred to as proofing, usually involves the production of proof prints, i.e. printouts of the data files, using a laser printer, a color printer or a similar low resolution device. The proof prints are then visually inspected so as to detect the correctness of the page impositions. The term imposition is commonly used to denote the correct sequential arrangement of pages that are to be printed, and also includes the proper alignment of page margins (sometimes referred to as registration). In books produced from a printing sheet having incorrect impositions, the margins on the front side and the rear side of a page may not coincide, or the sequence of the pages is not correct, for example.
When films are used to produce plates for the printing press, the films can be used for proofing purposes before the plates are imaged and printed. With the trend to eliminate films and to use “computer-to-plate” systems instead, films are not longer available for proofing.
In the printing industry special apparatus are used for the production of proof prints. These apparatus are sometimes referred to as pre-proofers and usually contain an arrangement of one or two printers which are used to sequentially print pages on a front and a rear side of a sheet of paper.